Deformable composite tubing comprising one or more tubular fluid conveyance lines or one or more tubular fluid conveyance lines disposed in heat transfer relationship to one or more heating lines having a thermal barrier disposed in encompassing relationship thereabout for maintenance or control of the conveyed fluid temperature is well known in the prior art. Such composite tubing may be used, for example, by the Chemical Processing Industry for maintaining or controlling the temperature of a fluid conveyed from a process line to a sampling or control instrument for the monitoring of selected properties such as viscosity or molecular weight. In many cases, accuracy of the measurements being taken may be adversely influenced when the temperature of the conveyed fluid is permitted to change during its course of travel from the process line to the sampling or control instrument. Other uses for such composite tubing may be, for example, the prevention of freezing or the heating of the conveyed fluid during its course of travel through the tubular fluid conveyance line of the composite tubing. Thermal barriers disposed about such deformable composite tubing provides a means of reducing costly energy loss which has lately become of increased importance in view of recent national and international energy conservation programs. Composite tubing of the nature described has been disclosed in U.S. Pat. No. 3,269,422 in which the thermal barrier is described as a Dacron-asbestos laminate or a pre-formed or cast expanded foam material. U.S. Pat. No. 3,315,703 also teaches that the insulating barrier or thermo barrier layer may be a laminated Dacron-asbestos and U.S. Pat. No. 3,355,572 describes the flexible thermo barrier layer of insulating material as a flexible cellular plastic or insulating tape. U.S. Pat. Nos. 3,522,413 and 3,727,029 teach other embodiments of composite tubing products without further defining thermal barriers over the prior art heretofore described. U.S. Pat. No. 3,853,149 teaches the use of rope-like organic and inorganic fibrous elements of high bulk and low density for use as thermal insulation and U.S. Pat. No. 2,578,280 merely describes a flexible insulation covering as being used as a binding mechanism.
Products made in accordance with the aforesaid patent references, however, provide certain undesirable characteristics such as low tear strength, increased stiffness, low moisture resistance, high chlorine content and low thermal efficiency associated with Dacron-asbestos laminates or high bulk, high compressibility, high deformation, enlargened diameter, lower melt or softening (with subsequent deformation) and poor flame resistance normally associated with foamed plastic insulations or high bulk and enlarged diameters associated with rope-like organic and inorganic insulations.